Divergence of localization length in short-range correlated superlattices

We study the localization/delocalization property of disordered GaAs–AlxGa1−xAs semiconductor superlattices with structural short-range correlations (so-called random-dimer model). Our system consists of square quantum barriers and wells with the same thickness and the heights of barriers have two different values. Using transfer matrix method, we calculate localization length of the system and show that there are two different delocalized states in the system. The energy of these extended states depends on the fraction of Al in the barriers. Then, we consider the divergence of the localization length near the extended state.